In the past, endoscope systems have been widely employed in diagnosis or observation of a body cavity or a thin lumen. An endoscope has an insertion unit that is inserted into the body cavity or thin lumen, and an operating unit for use in inserting the insertion unit in line with the internal shape of the body cavity or thin lumen. A light guide over which illumination light is guided, an image guide over which object light that is reflected light of the illumination light is guided, and the like are run through the operating unit and insertion unit alike. Moreover, the operating unit has an eyepiece member through which the object light guided over the image guide is viewed with naked eyes and a connector via which the light source device that supplies a predetermined amount of illumination light to the light guide is connected.
In recent years, electronic endoscope systems have been used in practice. The electronic endoscope system has a solid-state imaging device incorporated in the distal portion of the insertion unit or has a TV camera mounted on an eyepiece member of the operating unit. The solid-state imaging device or TV camera picks up object light that is reflected light of illumination light irradiated from the light guide, and produces an electronic image signal. After the electronic image signal is processed, an image is displayed on a monitor according to the resultant image signal.
When the endoscope system is used for diagnosis or observation, an amount of illumination light to be irradiated to a region to be diagnosed or observed, the wavelength thereof, and other operational conditions can be determined according to the region to be diagnosed or observed.
It takes much time to determine the operational conditions. In particular, it takes very much time to determine such operational conditions as a wavelength of illumination light and an amount thereof optimally to the region to be diagnosed or observed. Therefore, various operational conditions including the wavelength of illumination light and a magnitude of light regulation, which have been determined in order to perform diagnosis or observation using an endoscope system, are stored in a memory. When the endoscope system is used next, the previously determined operational conditions are read from the memory. Under the read operational conditions, the endoscope system is initialized so that diagnosis or observation can be performed. The initial operational conditions are modified optimally to a respective region to be diagnosed or observed. Endoscopic diagnosis or observation is then performed under the resultant operational conditions.
Consequently, the initial operational conditions under which the endoscope system performs diagnosis or observation can be determined quickly for a short period of time.
As mentioned above, the conventional endoscope system stores operational conditions, under which endoscopic diagnosis or observation has been performed, in a memory. When the endoscope system is reused for diagnosis or observation, the previous operational conditions are read from the memory and used to determine the initial operational conditions under which diagnosis or observation is performed next.
However, for example, assume that previous endoscopic diagnosis or observation is performed with a maximum amount of illumination light. After the diagnosis or observation is completed, when the driving power supply of an endoscope system is turned off, the operational conditions including an operational condition determined as the maximum amount of illumination light are stored in the memory.
After endoscopic diagnosis or observation is completed, when an endoscope is removed and put away, if the driving power supply is turned off by mistake with the maximum amount of illumination light adopted, the maximum amount of illumination light is stored in the memory.
Assuming that the endoscope system in which the previous operational conditions include the operational condition determined as the maximum amount of illumination light is used to diagnose or observe another region to be diagnosed or observed, when the driving power supply is turned on, the previous operational conditions are read from the memory. Consequently, the endoscope system is driven under the operational conditions including the operation condition determined as the maximum amount of illumination light.
Assume that a paramedic prepares the endoscope system, in which the maximum amount of illumination light has been adopted for the previous diagnosis or observation, for diagnosis or observation. After the driving power supply of the endoscope system is turned on, the endoscope system is left intact for some time until an operator actually starts endoscopic diagnosis or observation. Thus, a long time may elapse until actual diagnosis or observation starts.
In this case, the endoscope system is left intact with the maximum amount of illumination light adopted. The maximum amount of illumination light may heat, for example, a light guide connector that joins the light source device and endoscope system, an illumination lens located in front of the light guide at the distal end of the insertion unit of the endoscope system, or the insertion unit through which the light guide lies.
This poses a problem in that the heating deteriorates the light guide connector of the endoscope system, the illumination lens at the distal end of the insertion unit, or the insertion unit, or wastes driving power.
The electronic endoscope system has an automatic light regulation facility. Owing to the automatic light regulation facility, the luminance of an object image is calculated based on an object video signal produced by the solid-state imaging device, and an amount of illumination light to be supplied from the light source device is automatically controlled according to the calculated luminance. The automatic light regulation facility samples a luminance component from the object video signal produced by the solid-state imaging device. Based on the luminance component, the automatic light regulation facility performs light regulation by adjusting a diaphragm or a reduction filter located on the path of illumination light, controlling a lighting current that flows through a light source lamp, or the like.
In the electronic endoscope system, a communication cable linking a video processor that drives the solid-state imaging device so as to produce the object video signal, and the light source device that supplies illumination light to the endoscope system may be disconnected or incorrectly plugged in. Moreover, the communication facilities incorporated in the video processor and light source device may malfunction or fail. In this case, a luminance component is not transmitted from the video processor to the light source device. Consequently, the light source device determines that the object is the darkest. Consequently, driving is controlled in order to increase the amount of illumination light.
Accordingly, the amount of illumination light increases. Object light to be seen with naked eyes or electronically picked up is too bright to be used for diagnosis or observation. Moreover, the object light may cause heating.
The present invention attempts to break through the foregoing situation. An object of the present invention is to provide an illumination control system for endoscopes that even when the operational conditions determined for previous use include an operational condition determined as a maximum amount of illumination light, can adopt a suppressed amount of illumination light at the time of turning on a power supply. Thus, illumination light that is too bright to perform observation, heating, or wasting of driving power can be suppressed.
Another object of the present invention is to provide an illumination control system for endoscopes making it possible to automatically determine an optimal amount of illumination light for this time of endoscopic observation even when a previous operational condition is determined as a maximum amount of illumination light. Consequently, even if some time elapses from the instant preparations are made for endoscopic diagnosis or observation to the instant an operator actually performs endoscopic observation, heating will not occur. Thermal deterioration of an endoscope system can be alleviated.